One of the problems encountered in many tractor-trailer systems involves maintaining the air pressure in the tires. This is especially true when multiple sets of dual type wheels are used. A low pressure in one of the tires will often go undetected for long periods of time because the other wheels and tires in the vehicle are sufficient to support the loads.
Most drivers periodically check the tires of tractor-trailer vehicles during stop overs by tapping the tires with a tool. However, this precaution is sometimes overlooked and, in any case, not effective for detecting low pressure in a tire during operation between checks. In most cases, a driver has no warning when the pressure in one of a number of tires drops below a safe operating level while he is driving the vehicle. Such low pressures during operation may result from slow leaks in the tire, for example.
Low pressure in one of the tires during operation may cause any one of a number of serious problems. If the pressure in one of a group of tires is too low, it may cause the tire having the low pressure to spin because the tire does not make adequate traction with the road. This may cause the tire to heat up and possibly cause a fire. The spinning of the poorly inflated tire may also cause shredding and destruction of the tire which, if the low pressure were detected in time, could be recappable.
In a tire pressure and maintenance system in a tractor-trailer, it is desirable that the system utilize the source of pressure already available. Also, if for some reason the system fails, it is desirable to have independent means for inflating the tires and for detecting the pressure therein. It is also desirable in many cases to brake the vehicle to prevent movement thereof when a large leak in one of the tires develops.